A New York park honoring President Franklin D. Roosevelt, who used a wheelchair for years, is not fully accessible to disabled people, according to a class-action suit filed against the state and the conservancy that runs the park.

The strongly worded complaint, filed Thursday in federal court in Manhattan, accuses the Four Freedoms Park on Roosevelt Island of the “systemic, discriminatory exclusion” of people who use wheelchairs, scooters and other motorized devices from full access of the park. The complaint says that this is not only in violation of the Americans With Disabilities Act, which prohibits discriminating against people with disabilities in public facilities, but also violates state and local statutes.

“Such blatant violation of disability law is tragically ironic in light of the fact that President Roosevelt himself used a wheelchair for mobility after becoming paralyzed from polio,” the lawsuit states.

The four-acre park on the southern tip of the island was designed more than four decades ago by the renowned architect Louis Kahn, before the A.D.A. took effect. But construction did not begin until 2010, as the lawsuit notes, and it opened in 2013.

An elevated lawn lined with trees that forms a significant portion of the park’s space is accessible to wheelchairs from the far end of the park’s entrance, on paths of uneven paving stones, gravel and grass, the lawsuit charges.

“The combined effect of the increased distance, uneven surfaces, and vertical incline makes the monument substantially inaccessible to those with mobility disabilities.”

Nor is the gift shop fully accessible, nor the bathroom A.D.A. compliant, the suit says. And most strikingly, the terrace at the end of “the room” — an open granite enclosure at the southernmost tip of the park — that looks out over the East River is only accessible by stairs, and therefore “entirely inaccessible” to many disabled visitors.

The three individual plaintiffs named in the lawsuit — Phil Beder, Milagros Franco and Edith Prentiss — all use wheelchairs.

Ms. Prentiss felt like a “second-class citizen” after visiting that section of the park, the lawsuit notes; Ms. Franco left disappointed and angry; and Mr. Beder was deeply offended by the feature.

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A statue of President Franklin Delano Roosevelt at the Four Freedoms Park. The president used a wheelchair, crutches, braces or a cane for much of his adult life.CreditChang W. Lee/The New York Times

“I’m not a radical wheelchair-accessibility person — if a restaurant isn’t accessible I’ll find another one,” Mr. Beder, a retired teacher in Brooklyn, said in a telephone interview. “But when it comes to something like a memorial to a wheelchair-using president, it’s just insane that it wouldn’t be 100 percent accessible.”

Last year, the city clashed with the nonprofit conservancy behind the park over these accessibility issues, withholding a permanent certificate of occupancy and thousands of dollars of financing. The conservancy noted that some improvements had been made to Mr. Kahn’s original design and defended the final version.

Sally Minard, the president and chief executive of the conservancy, said at the time that the consequences of adding ramps to the terrace “seemed to outweigh the value.”

“The decision was not seen as a problem because we believed then, as we do now, that the park more than meets the requirements for accessibility for those with a disability, and that the memorial as a whole is A.D.A. compliant,” she said.

The lawsuit against Four Freedoms Park said that the park sets a troubling precedent.

“If it remains inaccessible, the precedent will be set whereby future architects will be free to design other public monuments and historic sites with zero regard for A.D.A. compliance,” the lawsuit said.

Michelle A. Caiola, the litigation director at Disability Rights Advocates, the nonprofit legal group that is representing the plaintiffs, said the group is looking for changes to the park, not financial compensation.

The Four Freedoms Park Conservancy said that it had not had time to review the lawsuit.

“The park has had thousands of visitors in wheelchairs, walkers, scooters, or other assistive devices who have enjoyed visiting the park and have found it accessible,” a spokeswoman said over email.

The state Office of Parks, Recreation and Historic Preservation did not return multiple requests for comment.

It’s not the first time a monument to President Roosevelt, who served between 1933 and 1945, has caused a heated discussion about disability.

A debate swirled around the National Park Service’s Roosevelt Monument a few years after the American With Disabilities Act was signed into law in 1990. The monument’s sculptures and bas-reliefs did not show Roosevelt using the wheelchair, crutches, braces or cane that he used for much of his adult life. A sculpture depicting Roosevelt in a wheelchair was added about four years after the park’s dedication.

A version of this article appears in print on , on Page A23 of the New York edition with the headline: Park in Roosevelt’s Name Marred by Bias, Suit Says. Order Reprints | Today’s Paper | Subscribe